Grinding wheel



Dec. 29, 1936. 5, LANE 2,065,942

. GRINDING WHEEL Filed March 21, 1936 Resihoid RUbber Abrasive aniCeramic Bond Resinoid u T mu Rubber }\W\\ Resinoid Patented Dec. 29,1936 UNITED STATES GRINDING WHEEL Merton B. Lane, Holden, Mass, asignorto Norton Company, Worcester, Mass., a corporation of MassachusettsApplication March 21, 1936, Serial No. 70,075

7 Claims.

This invention relates to grinding wheels and particularly to that typein which an abrasive body is cemented to a backing plate.

It is customary to cement a vitrified grinding wheel to a metal backingplate by means of rubber vulcanized to both the plate and the abrasivebody. It is, however, found that the rubber does not make a sufiicientlystrong union with the abrasive body and the backing plate for cer- 10tain grinding uses. Also, a vulcanized hard rubber has been employed asthe intermediate cementing material, but hard rubber tends to becomesoft at a high temperature.

The primary object of this invention is, therefore, to provide agrinding wheel of this type in which an abrasive body is united to a.backing plate by a resilient cementitious rubber compound which permitsthe necessary expansion and contraction, but in which the rubbercompound is itself secured to the abrasive body and/ or the backingplate by an intermediate cementitious material which has the capacity ofadhering firmly and strongly thereto and which is not thermoplastic ordetrimentally aifected by the high temperatures generated during anormal grinding operation and therefore serves to secure the abrasivebody to the backing plate firmly and prevents its becoming dislodged andbroken during use. Further objects will be apparent in the followingdisclosure.

In accordance with this invention, I propose to employ a vulcanized softresilient rubber compound as the primary medium for uniting the abrasivebody to a. backing plate, and particu- 5 larly to a metal plate, and tosecure this rubber compound to the abrasive body and/or the backingplate by an intermediate layer of a resinoid which is not thermoplastic,but is in a hard and infusible condition, and particularly a resinoid 49of the type formed by the reaction of phenol and formaldehyde as sold onthe market under such trade-marks as Bakelite and "Redmanol. In thiscase, the rubber gives the desired resilient mounting while the resinoidadheres firmly to the outer body and at the same time forms a strongunion with therubber.

For this purpose, I may employ a resinoid in what is known as the Bstage or in that plastic condition in which the material may be caused50 to adhere directly to the abrasive body and which may be thereafterheat hardened to an infusible condition known as the C stage at the sametime that the rubber is vulcanized. 0f the various different procedureswhich may be adopted, it

is preferred to use the resinoid in a liquid state,

such as a solution of the B stage, or the B material may be a dry powderwhich may be made plastic by heat below the temperature at which thematerial is converted to the C stage. Only a thin layer of the resinoidneeds to be employed, 5 and just sufiicient to adhere firmly andstrongly with the abrasive body and preferably not to fill the surfacepores thereof, although-it need not form an outer smooth layer on theface thereof. Likewise, a thin film of the resinoid may 10 be employed,if desired, in contact with the metal face to secure the rubber thereto.The intermediate rubber layer is preferably made up I of a vulcanizablesoft rubber compound containinga required amount of sulfur, such as 3%,as 15 well as other desired ingredients which are well known in theindustry.

I have illustrated in the drawing as a diagram matic showing twoembodiments of this invention in which:

Fig. 1 is a diametric sectional view of a. grinding wheel mounted on ametal plate, in which the resinoid is located between the rubber andboth the wheel and the metal plate.

Fig. 2 is an enlarged fragmentary section show- 25 ing the relations ofthe parts; and

Fig. 3 is an elevation of another wheel in which the resinoid is locatedonly between the rubber and the abrasive body.

The abrasive body may be madein accordance 30 with standard procedure.For example, it may comprise abrasive grains, such as crystallinealumina, silicon carbide, quartz or any other suitable abrasivematerial, cemented together into an integral structure by means of asuitable bond; 35 and preferably a vitrified ceramic bond which 4 hasbeen heat hardened to avitreous or porcelanic conditoin. This wheel asmade in accordance with standard procedm'e ordinarily comprises aconsiderable pore volume and a rough 49 surface with which theintermediate cementing compound may interlock and so adhere firmly andrigidly thereto.

If a resinoid, such as a Bakelite liquid resinoid in the B stage, is tobe employed, then this 45 liquid material may be painted or sprayed orotherwise applied to the surface pores of the abrasive body which hasbeen previously shaped as desired for mounting on the metal plate. Hiedry B stage powder may be mixed with the liquid to increase its resinoidcontent, A 'suificient amount of the fluid resinoid is applied to theface of the abrasive body so as to fill or partially fill the surfacepores to a desired extent and form a coating onthe porefacesaswellastheouter 55 face of the wheel. This layer is of sufficientthickness and strength so that it will, in turn, adhere firmly to therubber as well as to the abrasive body and make a desired strong uniontherewith. If a dry resinoid powder in the B stage is employed, then alayer of this material is sprinkled onto the surface of the abrasivebody and then later plasticlzed by heat, during the rubber vulcanizingoperation. The drawin is greatly exaggerated in order "to show thelayers, but it will be appreciated that these may be very thin, so thatwhen the final product has been completed, the abrasive body is veryclose to its metal backing plate; but separated themfrom by sumcientthickness of rubber and resinoid to give the desired properties ofresiliency as well as strength of union.

A layer of plastic unvulcanized rubber compound may be applied to thewheel face thus coated with the plastic or dry and unconverted resinoidor, if desired, the rubber coating may have been previously secured tothe face of the metal plate. Various sequences of operations arefeasible. I have found that excellent results follow from the use ofcompositions of the following formulae:

. I II Rubber "Parts by weight 29 40 Zinc oxide do 63 52 Magnesia do. 33 Sulfur do' 3 3 Oil of petrolatum do 2 2 Various solid materials, suchas carbon black,

- materials are folded into the rubber and thus gradually worked intoit. It is preferred that the rubber compound contain at least 40% byweight of zinc oxide, which improves the adhesive qualities of therubber layer, and this content of zinc oxide may well go as high as 70%to advantage. The rubber compound preferably contains only suflicientsulfur to form what is called a soft resilient rubber when in avulcanized condition. Hence, the flnal product is able to compensate forthe differential expansion and contraction between the abrasive body andthe metal plate as caused by heatchanges.

The metal plate is to be thoroughly cleaned and preferably roughened, asby means of a sand blast so that the rubber compound or resinoid willmake a very firm uniont'herewith. The soft rubber compound in theunvulcanized condition 18 pplied to the metal plate and the two thenplaced incontact with the resinoid coating on the abrasive body, afterwhich the assembled parts are subjected to suflicient heat and pressureto vulcanize the rubber and to convert the resinoid. This vulcanizationprocedure will serve to render a dry "Bakelite powder plastic and vforce. it into the pores of the abrasive body before it is converted andthus cause an intimate union between'the abrasive and the plasticunvulcanized rubber. Thereafter as the temperature rises, the reactionof vulcanization proceeds less.

body under pressure and heat. This rubber vulcanization and resinoidcuring operation may be accomplished by heating the assembled parts at va temperature of 160 C. for 16 hours and under a pressure of 30 lbs. persquare inch, more or In order that the invention may be more fullyunderstood, the following examples are to be Example I A steel plate wascleaned and sand blasted to provide a clean and rough surface, and asoft unvulcanized rubber compound containing rub ber, sulfur, zincoxide, magnesia, and petrolatum as defined in the first column of theabove table was applied thereto in a layer inch thick. This compound wasthen cured at about 160 C. by a suitable vulcanization process to formvulcanized soft rubber and it was found to adhere firmly to the metalplate. Thereafter, the exposed surface of the rubber was cleaned androughened as by means of a buihng wheel. Then the abrasive body ofsuitable composition and structure, which was to be cemented to themetal plate, was dusted heavily with a "Bakelite resinoid powder in theB stage so as to provide the layer intended to interlock with theabrasive as well as adhere to the rubber compound. The rubber coatedface of the metal supporting plate was then placed in contact with thisthick layer of Bakelite powder and gie assembled .structure wasgradually heated through a two-hour period to 160 C. and then wssubjected for sixteen hours to heat and pressure, at a temperature ofapproximately 160 C. to convert the Bake-- lite resinoid to a hardinfusible compound.

Example If The above procedure may be modified by employing a singleheat treatment operation instead of two. To that end, the abrasive bodymay be dusted over with the Bakelite" powder and the plastic layer ofunvulcanized rubber compound placed thereon with the sand blasted metalplate above it. Then, the rubber and the resinoid may be curedsimultaneously under pressure at a temperature of 160 C. for sixteenhours.

Example III In place of the "Bakelite" resinoid powder, one may employ aliquid Bakelite resinoid. In this case, the standard B stage liquid"Bakelite of commerce is coated upon the abrasive body to fill thesurface pores suiiiciently and to form a thin layer on the outer surfaceof the body, but which need not entirely fill the outer pores and form asmooth surface, since the rubher will squeeze into the irregularsurface-of the abrasive body. The layer of rubber compound as abovedefined may be placed upon this abrasive body and the metal plateapplied thereto,

Liquid"Bakelite" may be applied both to the sand blasted metal and tothe abrasive body. A layer of soft rubber compound 3', inch thick isplaced between and in contactwith-themlastic resinoid coatings. Then thebody L1 subjected to a pressure and heat treatment as above defined tovulcanize the rubber and convert the resinoid. In this case, theintermediate layer of rubber does not contact with either the abrasivebody or the metal plate, but only with the resinoid layers.

It is not known why the resinoidv makes a strong union with the rubbercompound, but it is to be noted that the standard resinoid contains aconsiderable quantity of he'xamethylenetetramine, which is also anaccelerator for rubber vulcanization. Hence, it is possible that thiscomponent of the resinoid in some way combines intimately with therubber to form a very complete union between the two layers. However,the claims are not to be interpreted as limited to any particular theoryof operation. It will be appreciated, also, that various otheringredients may be incorporated with the rubber or with the resinoid asdesired to serve as fillers or to give other properties of usefulness.Also, solvents for the dry resinoid may be employed to aid in itspenetration of the wheel pores,.such as furfural or other materialscapable of wetting the abrasive body and adhering to the resinoid, suchas a neutral creosote oil known on the market as carbosota, or kerosene,gasoline and the like or mixtures of these with furfural and othermaterials.

It will thus be seen that there has been provided by this invention anarticle in which the various objects hereinabove set forth together withmany thoroughly practical advantages are successfully achieved. Asvarious possible embodiments might be made of the mechanical features ofthe above invention and as the art herein described might be varied invarious parts, all without departing from the scope of the invention, itis to be understood that all matter hereinbefore set forth or shown inthe accompanying drawing is to be interpreted as illustrative and not ina limiting sense.

I claim:

1. A grinding wheel comprising an abrasive body cemented rigidly to abacking plate by an intermediate cemetitious medium including a layer ofvulcanized soft resilient rubber and a layer of converted resinoidbetween the rubber layer and one of the outer bodies.

2. A grinding wheel comprising an abrasive body cemented to a metalbacking plate by a cementitious medium including a layer of convertedresinoidcoating and adhering tov the surface of the abrasive body, alayer of vulcanized rubber compound adhering to the resinoid layer and ametal backing plate integrally connected with the intermediate rubberlayer.

3. A grinding wheel comprising an abrasive body cemented rigidly to abacking plate by an intermediate cementitious medium including a layerof vulcanized rubber secured to the abrasive body and a layer of aresinoid between the rubber and the metal plate and adhesively securingthem together.

4. A grinding wheel of the type covered by claim 2 in which a layer of aconverted resinoid is interposed between the vulcanized rubber compoundand the metal backing plate and insures firm union therebetween.

5. A grinding wheel having a porous body of ceramic bonded abrasivegrains united to a metal backing plate by a cementitious mediumcomprising a layer of converted resinoid impregnating the surface poresof one side of the abrasive body, a layer of soft, resilient vulcanizedrubber containing at least 40% by weight of zinc oxide which adheresboth to the resinoid coating and to the metal plate.

6. A grinding wheel having a porous body of ceramic bonded abrasivegrains united to a metal backing plate by a cementitious mediumcomprising an intermediate layer of soft resilient vulcanized rubber andlayers of a converted resinoid which adhere to the metal plate and thesurface of the abrasive body and are united with the rubber layer.

7. A grinding wheel of the type covered by claim 6 in which the rubberlayer contains at least 40% by weight of zinc oxide.

MERTON B. LANE.

